No abstract

Identifying effective methods to enhance the properties of catalysts is urgent to broaden the scanty technologies, so far. Herein, we synthesized four CoO crystals with different crystal planes and explored the crystal planes' effects on electrochemical water splitting through theoretical and experimental studies for the first time. The results illustrate that the correlation of catalytic activity is established as {111} > {112} > {110} > {001}. CoO crystals exposed with {111} facets show the highest OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) activities. Upon fabrication in an alkaline electrolyzer, the bifunctional {111}∥{111} couple manifests the highest catalytic activity and satisfying durability for overall water splitting. Density functional theory (DFT) explains that the {111} facet possesses the biggest dangling bond density, highest surface energy, and smallest absolute value of ΔG, leading to the enhanced electrocatalytic performance. This work will broaden our vision to improve the activity of various electrocatalysts by selectively exposing the specific crystal planes.

Inspired by the exquisite helices in Nature,f abrication of helical materials with controlled handedness has attracted considerable attention. Herein, we report on precis synthesis of single left-and right-handed helical polyisocyanides through living polymerization of achiral monomers using chiral palladium catalysts under helix-sense-selective manner.Mechanism study revealed that the yielded helices with opposite handedness showed different activity of the living chain end. The helix with unfavored handedness was selfterminated, while the one with favored handedness showed high activity and could undergo chain propagation to form ah igh molecular weight polymer with maintained singlehanded helicity.

electron-hole separation of CdS; [33][34][35][36][37][38] ii) PTCs can readily be prepared by comparable solvothermal reactions as porous materials and have already successfully been incorporated into metal-organic frameworks (MOFs); [39,40] and iii) the bandgaps and absorption properties of PTCs can be effectively modified by their surface organic ligands sensitization, [41][42][43] making it possible to tune the photocatalytic activities of the obtained composite materials by structural chemistry methods.On the basis of the above analysis, we have developed a stepwise solvothermal strategy to load a series of polyoxotitanium clusters into preformed CdS/MIL-101 composites to form new ternary PTC/CdS/MIL-101 materials (Scheme 1). The compositions and structures of these complex materials are confirmed by X-ray diffraction (XRD) analysis, inductively coupled plasma (ICP) analysis, and scanning and transmission electron microscopy (SEM and TEM). Visible-light-driven water splitting analysis indicates that the obtained ternary composites are all highly efficient H 2 -evolution photocalysts, even without noble metal as cocatalyst. Moreover, their activities can be significantly enhanced by increasing the conjugated effect of the organic ligands in PTCs, with the most aromatic, 1,1′-bi-2-naphthol, giving rise to the highest H 2 production rate of 94.9 mmol (g CdS h) −1 , which is over 50 times higher than that of the binary catalyst CdS/MIL-101.All ternary catalysts were prepared using typical three-step solvothermal reactions. First, pure phase, crystalline MIL-101 was achieved by a well-developed method reported in the literature. [32] Second, vacuum-activated samples of MIL-101 were treated with Cd(CH 3 COO) 2 ·2H 2 O and dimethylsulfoxide under 180 °C for 12 h to form CdS/MIL-101 composite materials. Third, the synthesized binary CdS/MIL-101 samples were added to the solvothermal reactions that could assemble pure PTCs, [Ti 6 O 4 (OiPr) 10 (O 3 P-Phen) 2 (L) 2 ] (L = isonicotinic for PTC-3, L = benzoic for PTC-7, L = bromoacetic for PTC-9, L = nitrate for PTC-18) and [Ti 4 (OH) 4 (L) 6 ] (L = R-1,1′-bi-2-naphthol for PTC-19) ( Figure S1, Supporting Information), to give rise to the final ternary PTC/CdS/MIL-101 catalysts. XRD patterns of the obtained ternary materials were recorded (Figure 1d and Figure S2-S7, Supporting Information). For these samples, a group of strong diffraction peaks before 20° can be well matched with the simulated MIL-101 signals, proving that the structure of MIL-101 was well retained after CdS and PTC loading. Three diffraction peaks with 2θ values at 26.5°, 44°, and 52.1° are related to the (111), (220), and (311) crystal planes of cubic CdS, respectively. Although some diffraction signals of PTCs were overlapped by those of MIL-101, many characteristic peaks can still be identified, confirming the formation of PTC components. Therefore, a range of ternary PTC/CdS/MIL-101 Photocatalytic hydrogen evolution by water splitting has been recognized as one of the most promising solutions to th...